The use of industrial retractable stop products has become wide spread, due at least in part to high demands in the automotive and heavy equipment industries. Conventionally, the retractable stops are powered by a linear actuator such as an air or hydraulic cylinder, or a solenoid actuator.
A power operated retractable stop assembly typically includes a reciprocatable rod member driven by the linear actuator, and an assembly body secured to the driving cylinder. Some of these existing assemblies, such as those described in U.S. Pat. No. 4,184,579, utilize a stop lever for stopping and releasing loads traveling on a conveyor. In such an assembly, a blocker leg is used to prevent pivoting of the stop arm causing an uncushioned "hard" stop of loads traveling on the conveyor, when the blocker leg is in the blocking position.
Other existing assemblies attempt to provide a cushioned stop by using cylinder pressure to hold the stop arm in the blocking position. However, assemblies such as these may be disadvantageous in that there is no guarantee of a stop, and a heavy load may deflect the stop lever against the biasing cylinder pressure and continue right past the retractable stop without stopping. Sometimes, assemblies utilize a first mechanism for actuating and deactuating the stop and utilize a separate shock absorber mechanism, such as the assembly described in U.S. Pat. No. 5,168,976.
Although these existing retractable stop assemblies that provide a "hard" stop and those assemblies that attempt to provide a cushioned stop by using cylinder pressure have been used in many applications that have been commercially successful, these assemblies have disadvantages. As in some applications it may be desirable to provide a cushioned stop, assemblies providing a "hard" stop without any cushion may not be desired. Further, although a cushion may be desirable in some applications, because such assemblies cannot guarantee a stopping of the load after the cushion, these assemblies too may be undesirable. Further, assemblies utilizing a separate shock absorber mechanism are complex and costly.
For the forgoing reasons, there is a need for an improved power operated retractable clamp assembly.